Calomel
Calomel (kal"o*mel) , noun
[Greek kalo`s beautiful + me`las black. So called from its being white, though made from a black mixture of mercury and corrosive sublimate. Compare French calomélas.]
(Chemistry) Mild chloride of mercury, Hg2Cl2, a heavy, white or yellowish white substance, insoluble and tasteless, much used in medicine as a mercurial and purgative; mercurous chloride. It occurs native as the mineral horn quicksilver.